Question

The initial charges on three identical metal spheres are the following: sphere A, +Q; sphere B, – Q/3; sphere C, +Q/3, where Q = 4.0 × 10–11 C. Spheres A and B are fixed in place, with a center-to-center separation of d = 0.8 meters, which is much larger than the spheres. Sphere C is touched first to sphere A, then to sphere B, and is then removed. What then is the magnitude of the electrostatic force between spheres A and B? Is the force attractive or repulsive?

Answer 1

First we calculate what will be the charge on A after C is touched with A,

then we calculate charge on B after C is touched with B,

Then we calculate force using coulomb's law,

and finally we find the nature of the force.